Speed changing mechanism



Feb. l, 1938. T'. R. GoLDsBoRoUGl-l SPEED CHANGING MECHANISM Filed Jan. 30, 1932 'n INVENTOR. ThaddeusRGoldsb orough @www Patented Feb. 1, l1938 VPATEN'I' oFFlc-n aiosns SPEED CHANGING MacnANlsM Thaddeus R. Goldsborough, Merc-hantvllle, N. J., assigner to Radio Corporation of America, a

corporation of Delaware .l Application January so, 1932, serial N. 589,968

2 claims. l (01. 274-9) v My invention relates to power transmission mechanism, and, more particularly to mechanism for transmitting power from a phonograph driving shaft or spindle, operating at one speed, to a record support, operating at another speed.

Until recently, substantially al1 phonographs of the disc-record type have been so designed that the turntables or record supports thereof rotate 'at 'I8 revolutions per minute. By reason of improved recording and reproducing methods, however, phonograph records requiring a much lower angular speed as, for example, 33%; revolutions per minute during sound reproduction, are now available. Obviously, such records cannot, satisfactorily, be reproduced on the majority of existing phonographs since the speed regulating mechanisms thereof cannot be adjusted to maintain the yextreme constancy of angular velocity required by the new slow-speed records, better known as long-playing records.

It is, of course, possible to so completely redesign or alter the mechanism of a phonograph that it will handle either standard records operable at '78 R. P. M. or long-playing records oper-` able at 331/3 R. P. M., and, in fact, such phonographs already are commercially available. Many people, however, cannot afford to discard their present phonographs in favor of the new dualspeed machines and thus are deprived of the pleasure of owning and enjoying, on their own machines, the new long-playing records now available to the public. f

It is, accordingly, an object of my invention to provide inexpensive means whereby slow-speed, long-playing records may be vreproduced on existlng phonographs designed for the standard high-speed records.

. A further object of vmy inventionis to provide an inexpensive attachment for existing phonographs whereby either standard or the new longplaying records may be reproduced at will.

Another object of my invention is to provide a record support or turntable which is interchangeable with the turntable of a standard phonograph whereby the new long-playing records may be reproduced on existing high speed phonographs.

A further object of my invention is to provide Aa turntable interchangeable with astandard turntable whereby the normal reproducing speed of standard phonographs may be changed to another predetermined speed without in any way altering the turntable spindle, the normal speed thereof,

vlor the motor-board of such phonographs,

record supports or turntables and having an automatic speed changingmechanism permanently attached thereto whereby, when said turntable is substituted for a standard record support operable at one predetermined constant speed, another predetermined constant speed is available.

A further object of my invention is to provide a turntable which is interchangeable with the turntable normally forming a part of a. standard phonograph whereby the normal reproducing speed of said phonograph is changed to another predetermined reproducing speed withoutchanging the speed of -the phonograph motor' or the turntable supporting spindle driven by the motor.

Another object of my invention is to change the of automatically changing the normalreproduc-` ing speed of the phonograph to another reproducing .speed without altering the speed of the turntable supporting spindle of the phonograph.

Another object of my invention is to provide a turntable interchangeable with the turntable of a standard type of disc phonograph whereby, when the said turntable is mounted on the turntable supporting spindle and the phonograph placed in operation, the new turntable will be rotated relatively to the spindle.

A further object of myinvention is` to transform standard phonograph's having but a single operating speed into plural speed phonographs whereby the normal reproducing speed thereof may be changed to another reproducing speed by removing the turntable on the phonograph and substituting a turntable'constructed in accordance with my invention in place thereof.

Other objects of my invention will become evident from the following detailed description taken in conjunction with the accompanying drawing, in

. which Figure l is a sectional assembly view of a turntable carrying a speed reducing mechanism iny accordance with my invention and mounted on the turntable spindle of a disc .phonograph of a conventional type, and

Fig. 2 is 'a perspective view illustrating the va'- rious parts comprising-.the speed changing mechanism and turntable in tion, and

Fig. 3 is a bottom plan view of the 'interchangeable turntable and speed changing mechanism detached, operative relaforming a part thereof.

Referring more particularly to the drawing, wherein similar reference characters indicate corresponding parts throughout, a motor-board I6 having a central clearance 'opening I I therein'and a turntable supporting spindle I2 carrying a driving pin I3 and extending vertically through the opening II, form parts of a conventional type of disc phonograph', and are shown to illustrate the application of my invention thereto.

In accordance with my invention, a record supporting disc or platen I4, forming a turntable of conventional design, is'provided with a centrally depending hubor boss I5 having a central bore I6 which extends through the hub Ii for the free vpassage therethrough o'f the spindle I2, as clearly shown in Fig. l.

Formed concentrically with the hub I5 adjacent the underside of the disc or platen il is a shoulder I6' on which an annular driving member II is suitably staked,` welded or otherwise secured, with the annular wall I3 of said driving'member depending from the shoulder I6 in spaced relation to the periphery of the hub I6. Formed in the annular wall of the member I1 are -a plurality of equally spaced, lvertically arranged slots |3-which extend inwardly from the lowermost peripheral edge of the said wall to a point substantially intermediate the vlength of the said drivy ing member.

' Rotatably mounted on the lowe end of the turntable boss or hub I 6. is a counterboredl sleeve 26 having a relatively smaller bore .2| in the-lowermost end thereof in axial alignment with the larger uppermost bore 22, the bore' 2| being of the same size as the bore I6 so that the bore I6 and 22 will register for the sliding passage therethrough of the spindle I2. A shoulder 23, formed in the sleeve 26 by they diering diameters of the axially aligned bores I6 ,and 22,

is provided with a suitable washer upon which the bottom face of the hub il seats.

Longitudinal movement of the counter-bored sleeve 26 on the hub Il is'prevented after placement thereon by means of` an onset locking pin 2l which so extends transversely through the sleeve 26 that the intermediate portion of the pin 2l will register with an annular groove 26 formed in the periphery'of the hub Il adjacent its lower free end, as clearly shown in Fig. 1. The

counter-boredsleeve 26 is further provided with a'transverse slot 2I'which is cut centrally across the bottom facethereof and is adapted to receive the driving pin I3 carried bythe spindle I2,

whereby the sleeve 26 is rotated in response to the spindle I2 and is supported against-further downward movement thereon in a manner well shoulder 32 on the sleeve y26 to insure the rotation of Athe inner raceway 23 with the sleeve 26. The annular driving member II depends in the space between the inner and outer raceways/29 and 36,

portion l respectively, which space is maintained by the against rotation. To this end, a split c ollar 33 may be suitably clamped about the periphery of the outer raceway 36 by means of a small screw bolt 34. A laterally extending ear or tab. 35, formed on the split collar 33 at a point diametrically opposite to its split ends, is provided for spot welding or otherwise securing a resilient restraining' member 36 thereto, as clearly shown in Figs. 1 and 2, the said member 36 having its free end bent downwardly for engagement with the top surface of the motor-board I6 when the turntable I4, together with the speed changing mechanism carried thereby, is placed on the spindle I2.

The bent portion of the member 36 which en- -of the bearing assembly 28 must be restrained vgages with the motor-board I6 may have a suitable notch 31 formed therein to provide a plurality of pointed ends or teeth 33 adapted to slightly dig'into the surface of the motor-board,

whereby the outer raceway 36 is securely held against rotation.

The split collar 33 may be further provided with a plurality of earsor tabsv 39 which are formed integral with the collaron the upper and lower peripheral edges thereof, as clearly shown in Figs. 2 and 3. These tabsor ears 33 are adapted to be turned or bent over onthe peripheral edges of the outer raceway 36 to prevent upward or downward movement of the collar 33 on the raceway. Preferably, although not necessarily, a washer of feltv or other suitable material, not shown, may be held against the bottom face of the bearing assembly 28 by means of the tabs or ears 39 to close the space between the inner and outer raceways 23 and 36 occupiedby the balls 3| and to prevent the entry of foreign matter between the balls and the raceways, and the dropping of a lubricant supplied to the balls, onto the surface of the motor-board.

Referring again to Fig. 1, itwill be observed that the lower endportion of the hub I6 has its diameter slightly reduced to minimize friction between the hub IB-and the sleeve 26 since, in operation, the rotation of the turntable hub II is relative to that of the sleeve 26.

Operation Assume that a standard disc phonograph of conventional design, adapted primarily for the reproduction of standard record tablets operable, for satisfactory reproduction, at '78 revolutions per minute is available. Assume, also, that it is now desired to reproduce sound from another record tablet which was recorded at a much slower angular speed and is commercially known as a long-playing record operable, for satisfactory reproduction, at 33% revolutions per minute. 'Ihe turntable or record support normally forming a part of the phonograph is removed from the supporting spindle therefor and another turntable or record support, constructed in accordance'with my invention as herein described, is then placed on the turntable spindle in place of the first mentioned turntable.

Assuming, now, that the phonograph is in op- 75 eration, the turntable spindle will'rotate at its normal speed, namely 78 R. P. M. as before, but the turntable or record support now on the spindlewill rotate relatively to the spindle, or at approximately 331/3 R. P. M. This diierence in angular speed is caused by the counter-clockwise rotation of the balls 3i, which are of a predetermined size, about their axes relative to the raceway 29, which is being rotated at 78 R. P. M., and clockwise relative to the stationary raceway 30. The difference in circumference between the outer diameter of the raceway 29 and the inner diameter of the raceway 30 governs the dliference between the clockwise advance of the balls 3i relative to the clockwise advance of an imaginary fixed point on the raceway 29. It is obvious, of course, that in speaking of the inner and outer diameters of the raceways 29 and 30, respectively, reference is made to the diameters of the annular ball grooves therein.

While speed changing devices have been known and used for various purposes and ln various machines including phonographs; such devices have heretofore been subject to a distinct disadvantage, particularly in sound reproducing machines,

when constancy of speed is essential to prevent so called wows, or variations in pitch of the reproduced sound. -Variations of this sort are due, usually, to mechanical irregularities, such as irregularities in gear teeth, which cause momentary disturbances or variations in the angular speed of the record supporting member. It will be apparent, however, from a consideration of the foregoing description of my invention, that the possibilities of' "wou/s appearing in a machine equipped with my improved speed changing mechanism will be practically entirely eliminated because it contains no gear trains or other similar elements which are subject to mechanical irregularities, being made up of elements of which the accuracy of manufacture can be controlled.

Although I have shown and described a certain specific embodiment of my invention, I am fully aware that many modifications thereof are possible. Furthermore, although I have shown and described my invention as applied to a device for operating the turntable at a slower speed 5 thanthe spindle, itis possible to apply my'invention to devices for operating the turntable at a greater speed than that of the spindle. llltirther, it should be noted that in either case, the device comprising my invention changes the speed of.

the'turntable to a speed diiferent than that oi the spindle, thereby constituting a true speed changing mechanism. My invention. therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention: 1. In combination, a spindle operable ata predetermined speed, a record support rotatably mounted on said spindle, an annular ball race adapted to co-act with said balls whereby said support may be rotated relativelyl t'o said spindle.

2. In combination, a record supporting platen provided with an axially depending hub having a central bore, a cup-shape member encircling the y hub, means for substantially preventing relative 30 axial movement of hub and cup-shape member, an inner ball race carried by the cup-shape member. an outer ball race encircling the inner race, a ball cage afilxed to the platen and extending into the space between the several ball-races, a plurality of balls in the ball cage, means for preventing the outer race from rotating and means whereby, *whenl the hub is mounted upon a phonograph spindle, motion may be imparted to said hub vfrom the spindle and .the platen caused to rotate 40 at a speed less than the speed of the spindle.

THADDEUS R. GOLDSBOROUGH. 

